Single cones of a variety of vertebrates are to be investigated spectrophotometrically to determine the spectral characteristics of the pigments they contain in order to understand the role of pigments in color perception. Colored oil droplets will also be studied in cones of those species that have them. Recordings will be made from ganglion cells of the species studied by MSP in order to study the color coding produced by the neural layers of the retina. Linear and circular dichroism will be studied in single receptors in order to determine the state of the visual pigment molecules in the receptor membranes. Ionic fluxes across receptor membranes will be studied by means of radioactive tracers.